For comparison purposes, a thick heavy water ice target bombarded by accelerated deuterons yields 3E7 n/sec/uA beam current at 200 kev. They mention that yield goes as square of accelerating potential up to 1 Mev. I guess this means that the potential drop accelerator in "the Amateur Scientist" running D into a D20 target would be making bunches o' neuts because it is in this range (at least voltage wise, I don't know how much beam current you could get.. I get 25 uA from the VanDeGraaf at that voltage)